1. Technical Field
The present invention relates to a mobile communication system.
2. Background Art
FIG. 7 illustrates a transmission bearer configuration and a protocol stack for a U plane PDU (Protocol Data Unit) provided between a mobile station UE and a gateway device S-GW in an LTE scheme (Release. 8) standardized in 3GPP.
As illustrated in FIG. 7, the bearer is an EPS (Evolved Packet System) radio bearer for the mobile station UE provided between the mobile station UE and the radio base station eNB, and an S1 bearer for the mobile station UE provided between the gateway device S-GW and the radio base station eNB.
As illustrated in FIG. 7, the U plane PDU (data signal) is configured to be transmitted/received between the gateway device S-GW and the mobile station UE on the EPS bearer (E-RAB) for the mobile station UE configured by the S1 bearer and the EPS radio bearer for the mobile station UE.
The mobile station UE is provided with radio bearer functions configured to set the EPS radio bearer for the mobile station UE with the radio base station eNB including a physical (PHY) layer function, an MAC (Media Access Control) layer function, an RLC (Radio Link Control) layer function, and a PDCP (Packet Data Convergence Protocol) layer function.
The radio base station eNB is provided with radio bearer functions configured to set the EPS radio bearer for the mobile station UE with the mobile station UE including a physical (PHY) layer function, an MAC layer function, an RLC layer function, and a PDCP layer function.
The radio base station eNB further includes S1 bearer functions configured to set the S1 bearer for the mobile station UE with the gateway device S-GW including a network 1/2 (NW L1/L2) function, an IP (Internet Protocol) layer function, a UDP (User Datagram Protocol) layer function, and a GTP (GPRS Tunneling Protocol)-U layer function.
Similarly, the gateway device S-GW is provided with S1 bearer functions configured to set the S1 bearer for the mobile station UE with the radio base station eNB including a network 1/2 (NW L1/L2) function, an IP layer function, a UDP layer function, and a GTP-U layer function.
In an LTE-advanced mobile communication system that is a next-generation communication scheme for an LTE scheme, a “relay node (RN)” including the same functions as the radio base station eNB can be connected between the mobile station UE and the radio base station eNB.
However, in a conventional mobile communication system, the mobile station UE is not adapted to execute transmitting/receiving a U plane PDU with the gateway device S-GW via one or a plurality of radio relay stations (an apparatus including a function of relaying a U plane PDU that is received via a radio bearer). Consequently, when a relay node RN including a radio relay station function is employed, application is not enabled for a protocol stack and a transmission bearer configuration for the U plane PDU as described above.